/*
* @(#)Deflater.java 1.42 05/08/09
*
* Copyright 2005 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.util.zip;
/**
* This class provides support for general purpose compression using the
* popular ZLIB compression library. The ZLIB compression library was
* initially developed as part of the PNG graphics standard and is not
* protected by patents. It is fully described in the specifications at
* the <a href="package-summary.html#package_description">java.util.zip
* package description</a>.
*
* <p>The following code fragment demonstrates a trivial compression
* and decompression of a string using <tt>Deflater</tt> and
* <tt>Inflater</tt>.
*
* <blockquote><pre>
* // Encode a String into bytes
* String inputString = "blahblahblah\u20AC\u20AC";
* byte[] input = inputString.getBytes("UTF-8");
*
* // Compress the bytes
* byte[] output = new byte[100];
* Deflater compresser = new Deflater();
* compresser.setInput(input);
* compresser.finish();
* int compressedDataLength = compresser.deflate(output);
*
* // Decompress the bytes
* Inflater decompresser = new Inflater();
* decompresser.setInput(output, 0, compressedDataLength);
* byte[] result = new byte[100];
* int resultLength = decompresser.inflate(result);
* decompresser.end();
*
* // Decode the bytes into a String
* String outputString = new String(result, 0, resultLength, "UTF-8");
* </pre></blockquote>
*
* @see Inflater
* @version 1.42, 08/09/05
* @author David Connelly
*/
public
class Deflater {
private long strm;
private byte[] buf = new byte[0];
private int off, len;
private int level, strategy;
private boolean setParams;
private boolean finish, finished;
/**
* Compression method for the deflate algorithm (the only one currently
* supported).
*/
public static final int DEFLATED = 8;
/**
* Compression level for no compression.
*/
public static final int NO_COMPRESSION = 0;
/**
* Compression level for fastest compression.
*/
public static final int BEST_SPEED = 1;
/**
* Compression level for best compression.
*/
public static final int BEST_COMPRESSION = 9;
/**
* Default compression level.
*/
public static final int DEFAULT_COMPRESSION = -1;
/**
* Compression strategy best used for data consisting mostly of small
* values with a somewhat random distribution. Forces more Huffman coding
* and less string matching.
*/
public static final int FILTERED = 1;
/**
* Compression strategy for Huffman coding only.
*/
public static final int HUFFMAN_ONLY = 2;
/**
* Default compression strategy.
*/
public static final int DEFAULT_STRATEGY = 0;
static {
/* Zip library is loaded from System.initializeSystemClass */
initIDs();
}
/**
* Creates a new compressor using the specified compression level.
* If 'nowrap' is true then the ZLIB header and checksum fields will
* not be used in order to support the compression format used in
* both GZIP and PKZIP.
* @param level the compression level (0-9)
* @param nowrap if true then use GZIP compatible compression
*/
public Deflater(int level, boolean nowrap) {
this.level = level;
this.strategy = DEFAULT_STRATEGY;
strm = init(level, DEFAULT_STRATEGY, nowrap);
}
/**
* Creates a new compressor using the specified compression level.
* Compressed data will be generated in ZLIB format.
* @param level the compression level (0-9)
*/
public Deflater(int level) {
this(level, false);
}
/**
* Creates a new compressor with the default compression level.
* Compressed data will be generated in ZLIB format.
*/
public Deflater() {
this(DEFAULT_COMPRESSION, false);
}
/**
* Sets input data for compression. This should be called whenever
* needsInput() returns true indicating that more input data is required.
* @param b the input data bytes
* @param off the start offset of the data
* @param len the length of the data
* @see Deflater#needsInput
*/
public synchronized void setInput(byte[] b, int off, int len) {
if (b== null) {
throw new NullPointerException();
}
if (off < 0 || len < 0 || off > b.length - len) {
throw new ArrayIndexOutOfBoundsException();
}
this.buf = b;
this.off = off;
this.len = len;
}
/**
* Sets input data for compression. This should be called whenever
* needsInput() returns true indicating that more input data is required.
* @param b the input data bytes
* @see Deflater#needsInput
*/
public void setInput(byte[] b) {
setInput(b, 0, b.length);
}
/**
* Sets preset dictionary for compression. A preset dictionary is used
* when the history buffer can be predetermined. When the data is later
* uncompressed with Inflater.inflate(), Inflater.getAdler() can be called
* in order to get the Adler-32 value of the dictionary required for
* decompression.
* @param b the dictionary data bytes
* @param off the start offset of the data
* @param len the length of the data
* @see Inflater#inflate
* @see Inflater#getAdler
*/
public synchronized void setDictionary(byte[] b, int off, int len) {
if (strm == 0 || b == null) {
throw new NullPointerException();
}
if (off < 0 || len < 0 || off > b.length - len) {
throw new ArrayIndexOutOfBoundsException();
}
setDictionary(strm, b, off, len);
}
/**
* Sets preset dictionary for compression. A preset dictionary is used
* when the history buffer can be predetermined. When the data is later
* uncompressed with Inflater.inflate(), Inflater.getAdler() can be called
* in order to get the Adler-32 value of the dictionary required for
* decompression.
* @param b the dictionary data bytes
* @see Inflater#inflate
* @see Inflater#getAdler
*/
public void setDictionary(byte[] b) {
setDictionary(b, 0, b.length);
}
/**
* Sets the compression strategy to the specified value.
* @param strategy the new compression strategy
* @exception IllegalArgumentException if the compression strategy is
* invalid
*/
public synchronized void setStrategy(int strategy) {
switch (strategy) {
case DEFAULT_STRATEGY:
case FILTERED:
case HUFFMAN_ONLY:
break;
default:
throw new IllegalArgumentException();
}
if (this.strategy != strategy) {
this.strategy = strategy;
setParams = true;
}
}
/**
* Sets the current compression level to the specified value.
* @param level the new compression level (0-9)
* @exception IllegalArgumentException if the compression level is invalid
*/
public synchronized void setLevel(int level) {
if ((level < 0 || level > 9) && level != DEFAULT_COMPRESSION) {
throw new IllegalArgumentException("invalid compression level");
}
if (this.level != level) {
this.level = level;
setParams = true;
}
}
/**
* Returns true if the input data buffer is empty and setInput()
* should be called in order to provide more input.
* @return true if the input data buffer is empty and setInput()
* should be called in order to provide more input
*/
public boolean needsInput() {
return len <= 0;
}
/**
* When called, indicates that compression should end with the current
* contents of the input buffer.
*/
public synchronized void finish() {
finish = true;
}
/**
* Returns true if the end of the compressed data output stream has
* been reached.
* @return true if the end of the compressed data output stream has
* been reached
*/
public synchronized boolean finished() {
return finished;
}
/**
* Fills specified buffer with compressed data. Returns actual number
* of bytes of compressed data. A return value of 0 indicates that
* needsInput() should be called in order to determine if more input
* data is required.
* @param b the buffer for the compressed data
* @param off the start offset of the data
* @param len the maximum number of bytes of compressed data
* @return the actual number of bytes of compressed data
*/
public synchronized int deflate(byte[] b, int off, int len) {
if (b == null) {
throw new NullPointerException();
}
if (off < 0 || len < 0 || off > b.length - len) {
throw new ArrayIndexOutOfBoundsException();
}
return deflateBytes(b, off, len);
}
/**
* Fills specified buffer with compressed data. Returns actual number
* of bytes of compressed data. A return value of 0 indicates that
* needsInput() should be called in order to determine if more input
* data is required.
* @param b the buffer for the compressed data
* @return the actual number of bytes of compressed data
*/
public int deflate(byte[] b) {
return deflate(b, 0, b.length);
}
/**
* Returns the ADLER-32 value of the uncompressed data.
* @return the ADLER-32 value of the uncompressed data
*/
public synchronized int getAdler() {
ensureOpen();
return getAdler(strm);
}
/**
* Returns the total number of uncompressed bytes input so far.
*
* <p>Since the number of bytes may be greater than
* Integer.MAX_VALUE, the {@link #getBytesRead()} method is now
* the preferred means of obtaining this information.</p>
*
* @return the total number of uncompressed bytes input so far
*/
public int getTotalIn() {
return (int) getBytesRead();
}
/**
* Returns the total number of uncompressed bytes input so far.</p>
*
* @return the total (non-negative) number of uncompressed bytes input so far
*/
public synchronized long getBytesRead() {
ensureOpen();
return getBytesRead(strm);
}
/**
* Returns the total number of compressed bytes output so far.
*
* <p>Since the number of bytes may be greater than
* Integer.MAX_VALUE, the {@link #getBytesWritten()} method is now
* the preferred means of obtaining this information.</p>
*
* @return the total number of compressed bytes output so far
*/
public int getTotalOut() {
return (int) getBytesWritten();
}
/**
* Returns the total number of compressed bytes output so far.</p>
*
* @return the total (non-negative) number of compressed bytes output so far
*/
public synchronized long getBytesWritten() {
ensureOpen();
return getBytesWritten(strm);
}
/**
* Resets deflater so that a new set of input data can be processed.
* Keeps current compression level and strategy settings.
*/
public synchronized void reset() {
ensureOpen();
reset(strm);
finish = false;
finished = false;
off = len = 0;
}
/**
* Closes the compressor and discards any unprocessed input.
* This method should be called when the compressor is no longer
* being used, but will also be called automatically by the
* finalize() method. Once this method is called, the behavior
* of the Deflater object is undefined.
*/
public synchronized void end() {
if (strm != 0) {
end(strm);
strm = 0;
}
}
/**
* Closes the compressor when garbage is collected.
*/
protected void finalize() {
end();
}
private void ensureOpen() {
if (strm == 0)
throw new NullPointerException();
}
private static native void initIDs();
private native static long init(int level, int strategy, boolean nowrap);
private native static void setDictionary(long strm, byte[] b, int off,
int len);
private native int deflateBytes(byte[] b, int off, int len);
private native static int getAdler(long strm);
private native static long getBytesRead(long strm);
private native static long getBytesWritten(long strm);
private native static void reset(long strm);
private native static void end(long strm);
}
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